<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>canvas 简介</title>
    <style>
        canvas {
            border: 2px solid red;
        }
    </style>
</head>

<body>
    <canvas id="firstCanvas" width="500" height="500"></canvas>

    <script>
        var myCanvas = document.getElementById('firstCanvas');

        //创建context 对象 getContext() 方法返回一个用于在画布上绘图的
    </script>
</body>

</html>